With the development of industrial production, the pollution caused by fossil fuel is posing a growing threat to the living environment of human beings. NOx is another main source of atmospheric pollution, second only to SOx, and also the main cause of formation of acid rain and photochemical smog. It was noted by the China Environmental Report that the total emission of NOx in 2011 is 24.043 million tons, and 23.378 million in 2012, slightly lower than that in 2011. Control and treatment of NOx pollution are urgently needed. At present, selective catalytic reduction (SCR) is the mainstream technique for flue gas denitration in the world. However, the apparatuses are expensive; the investment cost is high, particularly the cost of catalysts takes 30% to 60% of the initial investment cost of the whole system; and the subsequent replacements caused by abrasion and contamination of the catalysts are even more costly. Due to the addition of an SCR device, the on-way resistance, partial resistance, and resistance caused by the catalysts are increased, the power consumption of the draft fan is increased, the negative pressure rises, and the wear is increased correspondingly; furthermore, the heat loss is increased, and the overall efficiency is decreased somewhat.
There are many types of waste gases in the waste gas generated in the boiler. Among those waste gases, sulfur- and nitrogen-containing compounds are most seriously harmful to human beings.
Acid rain and photochemical smog will be formed when those gases enter the air, thereby seriously destroying the ecological environment and resulting in huge economical loss.
The energy utilization efficiency in China is only 33%, which is 10% lower than that in the developed countries. The waste heat resource takes about 17% to 67% of the total amount of fuel consumption. Since the combustion of fossil fuel will generate a great of nitrogen oxides, the mass formation of acid rain will be caused. In order to effectively treat the pollutants to protect the ecological environment, denitration has become a very important industry technique. At the later stage of denitration, a very large amount of heat will be generated in the denitration furnace, and since the flue gas containing a very large amount of heat is exhausted to the atmosphere without being utilized, the heating efficiency of the boiler is decreased and the coal consumption of power generation is increased.